All these so called exploits can already be done without a second ship. A stockpile of rares wull earn you no more than you would have earned over the same period anyway. So that reason doesnt work.
It's just one of the illogical things that are done to us for no reason. I wonder if someone at FD is sabotaging the game by putting players off.
I can't see how it would work with rares either, but then again, i never traded rares.
I'd do it with regular commodities.
The station i currently use as a makeshift "home" is a large hi-tech.
It consistently spawns missions for certain items like computer components, food items and various metals.
Now, instead of fetching these things for each individual mission, i could store big amounts of each with very few runs.
T-6 full of coffee
T-6 full of computer components
T-6 full of Palladium
etc.
That way i could pretty much farm the BBS for rewards and standings, and at the same time have my "main ship" available to do other things (say Res farming for example),
instead of fetching small amounts of mission items individually.
And every time i return to the station, whichever mission item is required i'd likely have readily at hand.
I could also just sit at the station, and let the BBS refresh and pop new fetch-me missions which i could complete immediately.
It's "exploitable" alright, even though somebody else could probably describe it better than me.
It's FD considering it exploiting (as in unintended use of game mechanics, if it were a thing), not me.
Personally i think it would make for an interesting logistics and planning challenge, but from THEIR point of view i can understand why they don't allow for it.